a. Field of the Invention
The present invention relates generally to automatable liquid sampling, and more particularly to automatable liquid sampling devices and methods for transferring aliquots of dissolved samples of pharmaceutical tablets from a kettle to an autoinjector of a high pressure liquid chromatograph (HPLC).
b. Background of the Invention
In tablet dissolution testing, a tablet is placed within a kettle having dissolution media therein. At various times during the dissolution process an aliquot of dissolution media from the kettle is removed and tested, usually by HPLC, to determine the extent to which the tablet has dissolved therein.
Automated tablet dissolution devices have previously been known in the art:
SASDRA.TM., made by Technicon Instruments Corp has been marketed as an automated tablet dissolution device. The determinative step is ultraviolet absorption and depends strongly on fixed mixing channels to obtain a response that is on scale. To operate properly, a detergent must be added to all liquids flowing through the system. Generally sufficient volume is not available for the detector to reach "steady state" for a proper reading. In addition, delicate glass plumbing is required to interconnect the tubings. After reading, the aliquot is discarded and not available for confirmation by a second technique. Due to limited storage capacity the device is not well suited to analysis requiring more than 6 aliquots. In addition, the timer uses a plastic tape for programming which is very inconvenient and imprecise. The timer can only hold enough tape for about a 6 hour run. Only a single component may be determined.
A second device, made by Hansen Research, is similar to the one proposed in that the aliquots are deposited in an autoinjector carriage. However, in the Hansen Research design, the carriage must then be transferred manually to the autoinjector for determination. All aliquots must be collected before analysis may be performed. This unit is built about and dependent upon an effective autoinjector which, however, is not fully automatic since the operator must manually transfer the carriage to the injector after all aliquots have been collected. No provisions are made for depositing aliquots in sealed vials.